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Subject:
[DCHAS-L] OSHA Top 10
Date:
Oct 29, 2018 22:26 UTC
Author:
NEAL LANGERMAN <neal**At_Symbol_Here**CHEMICAL-SAFETY.COM>
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Subject:
Re: [DCHAS-L] Lab Design
Date:
Oct 29, 2018 23:05 UTC
Author:
Schroeder, Imke <ischroeder**At_Symbol_Here**EHS.UCLA.EDU>
From:
Monona Rossol <0000030664c37427-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU>
Subject:
Re: [DCHAS-L] Lab Design
Date:
Oct 29, 2018 23:01 UTC
Reply-To:
ACS Division of Chemical Health and Safety
In-Reply-To:
Re: [DCHAS-L] Lab Design
Absolutely true. But if you confine a deflagration such as in a closed room, grain elevator, or inside a dust collector, you will have an explosion. In fact, confine either reaction and stuff will fly.
The Tiawan deflagration occurred when people were dancing in and around the edges of a very large drained swimming pool. The sides of the area were totally open to the elements. So there was no explosion here at all, just a burn over that hurt and killed a lot of people.
Monona Rossol, M.S., M.F.A., Industrial Hygienist
President: Arts, Crafts & Theater Safety, Inc.
Safety Officer: Local USA829, IATSE
181 Thompson St., #23
New York, NY 10012 212-777-0062
-----Original Message-----
From: Tom Slavin <slavinosh**At_Symbol_Here**GMAIL.COM>
To: DCHAS-L <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Sent: Mon, Oct 29, 2018 6:04 pm
Subject: Re: [DCHAS-L] Lab Design
The difference between a deflagration or a detonation is the speed of the pressure wave. If the pressure wave moves at less than the speed of sound it is a deflagration, but if greater than the speed of sound it is a detonation. Why the speed of sound? Because sound involves compression and rarefaction of air and the sound wave travels as fast as the air will allow. In the case of an explosion, if the pressure wave moves faster than the air will allow (speed of sound) the air itself will create the confinement.
Tom Slavin
Good point. What they do is deflagrate. And when this happens in a confined space, the increase in volume during the burn causes the explosion. But deflagration itself can be a burn hazard to those near. Since starch and dye mixtures are used for some special effects, in training I show slides of the Taiwan pool party fire where these "Holi-like" powders in the air ignited in a venue that was open to the air (not confined) and over 500 people were hospitalized and 15 died from their burns.
I see chemistry demonstrations on the internet involving powders in the air, and I don't think they realize how easily this can get out of hand.
Aluminum has the added issue of being a very hot fire and water creates some hydrogen so the fire can be difficult to put out. Mix the aluminum powder with a little iron oxide and you can't put it out at all.
Betcha a nickle that if you are in a college, you can go into your theater and/or art department metal shops and see people cutting, grinding and polishing aluminum right along with iron and other metals and they are completely clueless about the fire issues. I even see these idiots cutting aluminum on a table saw that is connected to a dust collector full of wood and plastic dust. And some
Aluminum work belongs in its own separate shop with a special vacuum for cleanup that is approved for Group E dusts.
